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Thursday, Dec. 13, 2012 10:27 am

Rats!

Henson-Robinson Zoo gets a fascinating new species. It’s not a panda.

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Naked mole-rats won’t win any beauty contests, but they are unique in the animal world.
PHOTO BY BRUCE RUSHTON

Imagine being impervious to pain, immune to cancer and darn near immortal.

Then imagine, as one scribe once put it, looking like a penis with buck teeth.

That is the conundrum of the naked mole-rat, the newest resident of the Henson Robinson Zoo.

They are nearly blind, cold-blooded, neither moles nor rats and utterly bizarre, eating their own feces while living in colonies of as many as 300 beneath East Africa. But we all could learn something from naked mole-rats, and lots of smart people are trying.

“Usually, if you live in an underground burrow, the last thing you want to do is use up all your oxygen by sharing with 299 other guys,” says Thomas Park, a scientist at the University of Illinois at Chicago who has made a career out of studying naked mole-rats. “The trick to making that work is that they have to get along really well, and they do. Food sources are so scattered that they need to work in teams. The downside is, they use up all the oxygen pretty quickly and generate lots of carbon dioxide from breathing and ammonia from peeing.”

Park and his research team have found that naked mole-rats survive low oxygen conditions through a mechanism that allows them to keep cell-destroying calcium out of their brains. Human infants have the same ability, Park says, which explains why kids are more likely than adults to be revived after nearly drowning.

Naked mole-rats don’t give a hoot about ammonia. In a paper published in September, Park and a colleague reported that there was no activity in an area of the brain that is supposed to respond to pain when the critters loitered around sponges soaked with ammonia and acid solutions that caused lesser rodents to flee. Furthermore, unlike other mammals, their skin lacks a neurotransmitter called Substance P that carries pain signals to the brain.

Naked mole-rats do avoid extremely high concentrations of ammonia or acidic fumes, however, and they can feel some pain, Park says. He uses a hot-burner analogy: A naked mole-rat that touched a hot stove burner would experience pain intense enough that it would stop touching the burner, but once it was no longer in contact with the burner, it would feel fine. Put another way, if a naked mole-rat got an appendectomy, it would wake up from surgery feeling no pain.

It’s that sort of biochemistry that fascinates scientists who have mapped the genome of the naked mole-rat, hoping that the wunder rodent’s genetics might yield solutions to human ailments. Scientists have never found cancer in a naked mole-rat, even though researchers have injected heavy doses of carcinogens. They are also Noahs of the animal kingdom, living as long as 30 years, by far the longest lifespan for a rodent. Similarly sized mice or rats, by contrast, live less than five years.

“If I were a cancer, I wouldn’t want to be in that animal,” says Mike Stratton, executive director of the Springfield Park District. “They’re hideous.”

Ugly, perhaps, but a naked mole-rat is not stupid. Consider what it does when it finds something to eat, no small task given it is a near-sightless herbivore that lives in arid areas. Instead of completely devouring favored tubers and roots, naked mole-rats leave enough for the plant to survive so that they can come back for more once the plant has regenerated.

While not as sexy, perhaps, as pandas or belugas, naked mole-rats became popular in zoos within the past 20 years. They behave more like bees or ants than mammals, with each colony having a queen that doesn’t do much except eat, breed and nurse little naked mole-rats. There are also soldiers to defend against snakes while smaller workers gather food and do the digging. There is a definite pecking order, with soldiers always crawling on top of workers when encountering each other in a narrow passage. They huddle a lot, creating pink, breathing, cold-blooded piles of mole-rat.

Although decidedly un-fierce as they go about their business six feet or so below the surface, zoo director Talon Thornton has had to un-wedge a pair that got stuck when they tried to pass each other in an acrylic tube that passes for a subterranean tunnel.

“I was shaking that tube like a ketchup bottle,” Thornton recalls.

Park, who once studied bats, switched to mole-rats in the 1990s after first seeing them in a zoo.

“They’re a fantastic zoo exhibit because they live so long and they’re interesting,” Park says. “Kids get their noses right up to the glass.”

Contact Bruce Rushton at brushton@illinoistimes.com.

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